import { OnePagerSummary, ExamWarning, InfoCardGrid, InfoCard, MnemonicCard, EvidenceCard, VivaScenarioSection, VivaScenario, ExamCheatSheet, ContentSection, ExamPearl, SafetyAlert, Tabs, Tab, ComparisonTable } from '@/components/mdx' ## Indications **Revision Sacroiliac Arthrodesis:** - Failed posterior SI fusion with persistent pain and instability - Anterior column deficiency requiring supplemental anterior fixation - Pseudarthrosis after posterior-only fusion in high-demand patients **Anterior Pelvic Ring Injuries:** - Unstable anterior pelvic ring injury requiring direct ORIF - Crescent fracture with anterior SI joint involvement - Vertical shear injury (APC III, LC III) with anterior SI disruption - Failed closed reduction of rotational instability **Hardware-Related Issues:** - Prominent anterior SI screws causing nerve compression or vascular compromise - Removal of broken or misplaced anterior hardware - Revision fixation after hardware failure **Why Anterior Approach?** - Direct visualization of anterior SI joint and L5 nerve root - Allows placement of anterior column plate from ilium to sacrum - Can address anterior soft tissue pathology (scarring, nerve entrapment) - Necessary for certain revision arthrodesis techniques **Complex Revision Cases:** - Recurrent SI joint dislocation despite posterior fixation - Need to decompress L5 nerve root (compressed by callus, hardware, or scar) - Removal of heterotopic ossification around SI joint - Tumor resection involving anterior SI joint **Primary SI Arthrodesis (Rare):** - Some surgeons advocate anterior approach for primary arthrodesis in select cases - Allows better visualization of joint preparation - Theoretical advantage: compression across SI joint from anterior - However, most surgeons prefer posterior or percutaneous approaches for primary cases **Absolute:** - Active infection overlying surgical field - Patient medically unfit for prolonged complex pelvic surgery - Severe adhesions from multiple previous surgeries (relative) **Relative:** - Obesity (BMI more than 40) - extreme difficulty exposing SI joint - Previous radiation to pelvis (tissue quality poor) - Osteoporosis (poor screw purchase) - Pregnancy (relative - avoid if possible) **When to Use Posterior Approach Instead:** - Most primary SI pathology (fusion, fracture fixation) - Simpler, safer, better bone purchase - Reserve anterior approach for complex revision cases only ## Pre-operative Planning **History:** - Previous pelvic surgeries and approaches used - Mechanism of original injury (if trauma) - Symptoms: pain location, radiation, neurological symptoms - Failed treatments (conservative, posterior surgery) - Functional limitations **Examination:** - **Neurological exam CRITICAL:** - L5 nerve root function (EHL, ankle dorsiflexion, sensation dorsal foot) - S1 nerve root function (ankle plantarflexion, sensation sole) - Document baseline carefully - SI joint provocative tests (FABER, Gaenslen, thigh thrust) - Gait pattern - Leg length discrepancy (pelvic asymmetry) - Palpate for prominent hardware anteriorly **EXAM KEY:** "The anterior approach to SI joint is HIGH RISK. L5 nerve root injury occurs in 5-15% of cases and causes permanent foot drop. I only use this approach when absolutely necessary after posterior approaches have failed." **Plain Radiographs:** - AP pelvis - Inlet view (SI joint displacement) - Outlet view (vertical displacement) - Lateral sacrum - **Ferguson view** (AP with 30-degree cephalad tilt) - best shows SI joint **CT Scan (Essential):** - Fine-cut CT through SI joint (1mm slices) - 3D reconstruction - Assess: - SI joint morphology and bony anatomy - Presence of pseudarthrosis or nonunion - Position of previous hardware - Bone quality - Vascular anatomy (if contrast available) **MRI (Very Helpful):** - Assess soft tissue around SI joint - Identify scar tissue, nerve entrapment - Evaluate for infection (high T2 signal, enhancement) - Look for bone marrow edema (active inflammation) **Vascular Imaging (Consider):** - CT angiography if revision case with extensive scarring - Identifies aberrant iliac vessel anatomy - Maps collateral circulation - Helps plan safe corridor to SI joint **Expected Outcomes:** - Pain relief in 60-80% of revision arthrodesis cases - Fusion rate: 70-85% with anterior + posterior combined fixation - Functional improvement variable (depends on chronicity) **Specific Risks (HIGH):** | Complication | Rate | Details | |--------------|------|---------| | L5 nerve root injury | 5-15% | Foot drop, chronic pain, permanent in 50% | | Iliac vessel injury | 2-5% | Life-threatening, may require vascular surgery | | Lumbosacral plexus injury | 1-3% | Multiple nerve roots affected | | Infection | 5-10% | Higher than routine surgery | | Nonunion | 15-30% | Even with optimal technique | | Chronic pain | 20-40% | Revision cases have guarded prognosis | | Bowel/bladder injury | Less than 1% | Adhesions from previous surgery | **Alternative Treatments:** - Continue conservative management (PT, injections, bracing) - Repeat posterior approach with bone grafting - SI joint fusion with percutaneous techniques (iFuse, SI-BONE) - Pain management referral (chronic pain program) ## Equipment - Anterior SI plates (specialized designs) - 3.5mm pelvic reconstruction plates - 4.5mm lag screws (for joint compression) - Cannulated screws (7.0-7.3mm for percutaneous) - Structural bone graft (iliac crest autograft) - Allograft options (femoral head, cancellous chips) - Retractor set (Hohmann, malleable, visceral retractors) - Vascular instruments (have available) - Nerve dissection set (fine dissectors, vessel loops) - Pelvic reduction clamps - Curettes, osteotomes for joint preparation - Headlight (essential for deep pelvic exposure) - Fluoroscopy (C-arm, essential) - Cell saver - 4-6 units PRBC crossmatched - Vascular surgery backup on standby - Neurosurgical backup (if nerve decompression needed) - Nerve stimulator for L5 identification ## Anaesthesia and Positioning **Type:** General anaesthesia (mandatory) **Considerations:** - Prolonged case (2-4 hours typical) - Muscle relaxation essential - Arterial line for complex revision cases - Central venous access if anticipated vascular injury risk high **Adjuncts:** - Tranexamic acid 1g IV at induction - Broad-spectrum antibiotics (Cefazolin 2g + Gentamicin) - Cell saver - Warming blanket **Position:** Supine **Setup:** 1. Standard supine position on radiolucent table 2. Arms tucked or out on arm boards (surgeon preference) 3. Bump under ipsilateral buttock (15-20 degrees) - improves SI joint access 4. Hip slightly flexed and externally rotated 5. Ensure C-arm can access pelvis from multiple angles 6. Pressure points padded **Preparation:** - Prep from nipples to mid-thigh - Circumferential prep if iliac crest bone graft needed - Include entire abdomen (case may extend medially) - Drape to allow extension of incision if needed ## Surface Anatomy and Landmarks ## Surgical Approach The anterior approach to the SI joint does NOT use a traditional internervous plane. Instead, it requires: - **Modified ilioinguinal approach** (most common) OR - **Modified Stoppa approach** Both approaches involve extensive soft tissue mobilization and retraction of critical neurovascular structures including the lumbosacral plexus, iliac vessels, and pelvic viscera. This is NOT a routine approach. It is technically demanding and reserved for complex revision cases. ## Complete Step-by-Step Technique ### Step 1: Incision (Modified Ilioinguinal) **Configuration:** Ilioinguinal incision - Begin 2cm medial and superior to ASIS - Curve along iliac crest for 6-8cm - Then curve medially and inferiorly toward pubic tubercle - Stop at midline or extend to Pfannenstiel if wider exposure needed - Total length: 15-20cm **Layers:** 1. Skin and subcutaneous tissue 2. External oblique aponeurosis and fascia 3. Develop three windows (lateral, middle, medial) ### Step 2: Develop Lateral Window **Lateral Iliac Window:** 1. Incise external oblique along iliac crest 2. Elevate iliacus muscle from inner table of ilium 3. Identify lateral femoral cutaneous nerve (protect) 4. Expose inner pelvic brim **Purpose:** - Exposes iliac wing for bone graft harvest if needed - Provides lateral reference point - Rarely provides direct SI joint access (joint is too medial) ### Step 3: Develop Middle Window (Critical for SI Access) **Iliopectineal Window:** 1. Identify and protect femoral nerve (lateral border of psoas) 2. Identify iliac vessels (run on psoas, cross pelvic brim) 3. **Mobilize iliac vessels medially** (dangerous step): - Ligate and divide small branches - Use gentle vascular tapes for retraction - Avoid excessive traction (vessel injury) 4. Identify psoas muscle and retract laterally 5. This window provides access to sacral ala and anterior SI joint **EXTREME CAUTION:** The iliac vessels must be mobilized to access the anterior SI joint. This is dangerous: - Vessels are friable, especially in revision cases with scarring - Tearing common iliac vein = life-threatening hemorrhage - Always have vascular surgery backup available - Use gentle blunt dissection only - Have vascular clamps ready ### Step 4: Identify and Protect L5 Nerve Root **L5 Nerve Root - THE CRITICAL STRUCTURE:** 1. **Location:** - L5 nerve root emerges from L5/S1 foramen - Runs obliquely across sacral ala toward SI joint - Lies DIRECTLY on anterior SI joint capsule - Covered only by thin layer of fascia and periosteum 2. **Identification:** - After mobilizing iliac vessels medially, identify lumbosacral trunk - L5 nerve root is largest component - Feels like cord, approximately 5-8mm diameter - Use nerve stimulator to confirm (foot dorsiflexion at low voltage) 3. **Protection:** - Place blunt Hohmann retractor MEDIAL to nerve - Gently retract nerve laterally (extreme care - already at risk) - Minimize retraction time - Release retractor periodically - NEVER divide or cut nerve L5 nerve root injury is the most common and devastating complication of anterior SI approach (5-15% incidence). **Causes:** - Traction during retraction - Direct trauma from instruments - Thermal injury from drill/cautery - Compression from retractors **Result:** - Foot drop (EHL weakness, ankle dorsiflexion weakness) - Numbness dorsal foot and great toe - Chronic neuropathic pain - 50% have permanent deficits despite early recognition **Prevention:** - Minimize retraction - Use nerve stimulator to identify nerve before any drilling/cutting - Keep drill/cautery away from nerve - Constant awareness of nerve location ### Step 5: Expose Anterior SI Joint 1. After retracting L5 nerve root laterally and iliac vessels medially: - Palpate SI joint through thin capsule - Joint is approximately 1cm thick anteroposteriorly - Sacral ala is medial, ilium is lateral - Joint runs obliquely (superior-medial to inferior-lateral) 2. Use fluoroscopy to confirm joint location: - AP and outlet views - Place K-wire into joint under fluoroscopy to mark location 3. Capsulotomy: - Make longitudinal incision through anterior capsule - Stay sutures for later repair - Expose joint surfaces ### Step 6: Joint Preparation (If Fusion Intended) **For SI Arthrodesis:** 1. Use curettes to remove all cartilage from both surfaces 2. Expose bleeding subchondral bone 3. Fenestrate subchondral bone with small drill to enhance fusion 4. Pack joint with bone graft (autograft from iliac crest preferred) 5. Reduce joint with reduction clamps 6. Compress joint (anterior-to-posterior direction) ### Step 7: Apply Anterior Fixation **Plate Fixation (Preferred for Arthrodesis):** 1. Contour 3.5mm pelvic reconstruction plate 2. Position plate from ilium (lateral) to sacrum (medial) 3. Plate lies on anterior SI joint capsule 4. **CRITICAL:** Check L5 nerve root position before ANY drilling 5. Place screws into ilium (4-6 screws) 6. Place screws into sacral ala (2-4 screws) - Sacral screws challenging - poor bone quality - Aim for S1 body (best purchase) - Fluoroscopy essential (avoid L5/S1 foramen) 7. Confirm no hardware impingement on L5 nerve root **Screw Fixation (Alternative):** 1. Percutaneous or direct SI screws from ilium to sacrum 2. Placed under fluoroscopy guidance 3. Typically 2-3 screws 4. Each screw crosses SI joint ### Step 8: Final Assessment 1. Release all retractors 2. Inspect L5 nerve root (should be intact, normal appearance) 3. Check nerve stimulation (confirms function) 4. Assess iliac vessels (no injury, good flow) 5. Fluoroscopy all views (AP, inlet, outlet, lateral): - Confirm joint reduction - Check hardware position - Ensure no foraminal or canal encroachment ### Step 9: Closure **Critical Repairs:** 1. Repair anterior SI joint capsule with 0-Vicryl 2. Reconstruct pelvic floor if disrupted 3. Ensure iliac vessels in anatomic position **Layer Closure:** 1. Close external oblique and transversalis fascia (1-0 Vicryl) 2. Place deep drain (19Fr Blake) 3. Scarpa's fascia (2-0 Vicryl) 4. Skin (staples or 3-0 Monocryl) ## Intra-operative Complications **Rate:** 5-15% (most common serious complication) **Mechanisms:** - Traction injury from retractors - Direct laceration - Thermal injury - Compression from hardware **Recognition:** - Nerve stimulator shows loss of response - Visual inspection shows nerve damage - Post-operative foot drop **Management:** - If recognized intra-operatively: - Release all traction immediately - Inspect nerve for laceration - If lacerated: microsurgical repair (neurosurgery consult) - If intact: pad nerve, minimize further trauma - Post-operative: - EMG at 6 weeks - AFO for foot drop - Physiotherapy - Most improve partially over 6-18 months - 50% have permanent deficits **Rate:** 2-5% **Vessels at Risk:** - Common iliac artery and vein - Internal iliac vessels - External iliac vessels **Recognition:** - Sudden hemorrhage - Expanding hematoma - Hypotension **Management:** - **Immediate:** - Direct pressure with pack - Call vascular surgery immediately - Rapid fluid resuscitation - Activate massive transfusion protocol if severe - **Definitive:** - Vascular repair (primary repair if small tear) - Interposition graft if large defect - Ligation of internal iliac may be necessary (not ideal but life-saving) - Post-operative vascular monitoring **Prevention:** - Gentle dissection - Visualize vessels throughout - Have vascular surgery on standby for complex revisions **Rate:** 1-3% **Structures at Risk:** - L5 nerve root (most common) - S1 nerve root - Lumbosacral trunk - Obturator nerve (if dissection extends too far medially) **Recognition:** - Multiple nerve root deficits - Severe post-operative pain - Bladder/bowel dysfunction (if sacral roots involved) **Management:** - Most are traction injuries (neuropraxia) - Conservative management with observation - EMG at 6 weeks for prognostication - Neurosurgical consult if no improvement by 3-6 months **Rate:** Less than 1% **Mechanism:** - Adhesions from previous surgery - Inadvertent perforation during dissection **Recognition:** - Bowel contents or urine in field - Post-operative peritonitis **Management:** - Intra-operative recognition: primary repair by general surgery - Post-operative recognition: reoperation, diversion may be needed ## Post-operative Care **Day of Surgery:** - ICU monitoring (high-risk case) - **Neurological checks every 2 hours:** - L5 function (EHL, ankle dorsiflexion) - S1 function (ankle plantarflexion) - Document and compare to pre-operative baseline - Monitor for vascular complications (distal pulses, compartment syndrome) - Drain output monitoring - DVT prophylaxis: LMWH from Day 1 **Mobilization:** - **Bed rest 24-48 hours** (allow healing) - Log roll only - Avoid hip flexion more than 45 degrees (protects SI joint) **Weight Bearing:** - **Toe-touch weight bearing only** for 6-8 weeks - Walker or crutches - Gradual progression based on pain and X-ray evidence of healing **Restrictions:** - No sitting more than 30 minutes at a time (first 2 weeks) - No twisting or bending - No lifting more than 5kg **Wound Care:** - Remove drain when output less than 30ml/day (typically Day 2-4) - Sutures/staples out at 14-21 days **Imaging:** - X-ray at 2 weeks (AP pelvis, inlet, outlet) - Check hardware position, alignment **Weight Bearing Progression:** - Week 6: X-ray to assess healing - If healing progressing: advance to partial weight bearing (50%) - Week 10-12: Full weight bearing if radiographic fusion evident **Physiotherapy:** - Core strengthening - Pelvic stabilization exercises - Gait training - Avoid impact activities until 6 months **Return to Activities:** - Driving: 8-12 weeks (off narcotics, adequate control) - Sedentary work: 6-8 weeks - Manual labor: 4-6 months - Sports: 6-12 months **Follow-up:** - 6 weeks, 3 months, 6 months, 1 year - X-rays at each visit - CT at 6-12 months to confirm fusion **Fusion Assessment:** - Bridging bone across SI joint on CT - No hardware loosening or breakage - Clinical: pain-free weight bearing **Outcomes:** - Fusion rate: 70-85% with anterior + posterior combined - Pain relief: 60-80% in revision cases - Functional improvement variable - L5 nerve injury recovery: 50% permanent deficit rate ## Viva Scenarios ## Key Exam Points ## Evidence-Based Practice

Anterior Approach to Sacroiliac Joint

Anterior Approach to Sacroiliac Joint